The present invention is generally related to the preservation of seafood and other food products for consumer consumption, and more particularly is related to a process for preserving fish by treating fish with smoke and ozone to retard degradation of the fish and maintain the fresh-like appearance of the fish. Optionally, the fish can then be frozen to further prolong its shelf life
The preservation of fish has been a major concern for fishermen and fish processors for centuries. Originally man salted and dried fish to preserve it. Since the advent of mechanical refrigeration, the fish have been preserved by freezing and refrigeration, thus permitting fishermen to make longer fishing trips, as well as transport the fish long distances over land or water.
The length of time over which fish maintains its freshness is commonly referred to as its shelf life. The shelf life of fish is determined by a number of factors, including the total number of each type of bacteria initially present, the specific types of bacteria present, the temperature of the flesh of the fish and of the surrounding atmosphere, and the pH of the fish. It is known that to extend the shelf life of fish, one may, for example, reduce the number of bacteria present using chemical means, freezing or other methods, create an acidic pH and/or maintain the product below 5xc2x0 C. in its fresh state. The most common process employed to extend the shelf life of fish is freezing.
An inherent problem with freezing fish is its loss of the xe2x80x9cfreshxe2x80x9d attributes such as a xe2x80x9cpinkxe2x80x9d or xe2x80x9credxe2x80x9d meat color to both the fish flesh and the xe2x80x9cblood linexe2x80x9d in the fish. The loss of these attributes causes the value of the frozen fish to be much less than the value of fish that has not been previously frozen. This loss of value is an interpretation of the quality of the fish by the consumer. The color of the flesh and blood line of the fish is a major factor in the selling of seafood at the consumer level. Most consumers purchase fish with their xe2x80x9ceyesxe2x80x9d rather than with any other factor, such as smell, taste or texture. Therefore, it is desirable to maintain the xe2x80x9cfreshxe2x80x9d pink/red color of the seafood products as long as possible in order to sell the product at a premium to consumers.
Although many factors may effect changes to the color of fish products, the main reduction of color results from damage to the hemoglobin pigments in the fish. Several of the primary causes for the reduction of hemoglobin pigments, resulting in a corresponding reduction in the xe2x80x9cfreshxe2x80x9d color of the fish, include oxidation of the xe2x80x9credxe2x80x9d hemoglobin pigments in the flesh to a xe2x80x9cbrownxe2x80x9d color; bacterial decomposition of the cells containing the hemoglobin pigments; and destruction and oxidation of the hemoglobin pigment during freezing.
Most unfrozen fish is considered xe2x80x9cfreshxe2x80x9d for as many as 30 days from catching. However, unfrozen fish this old usually contains high levels of dangerous bacterial decomposition. Bacterial decomposition of fish is the cellular breakdown of the flesh of the fish due to the digestive enzymes of bacteria present on or within the flesh of the fish. Conversely, frozen fish is usually frozen upon catching which reduces the likelihood that the fish will contain significant or harmful levels of bacterial decomposition.
In order to preserve the freshness of the fish and maintain the color of the flesh and blood line to a satisfactory consumer level, processes using smoking and freezing techniques have been applied.
Smoking of fish has been one of the major forms of fish preservation for centuries. Smoking involves the burning of organic substances, such as wood, to produce a complex mix of over 400 separate chemical compounds. These compounds, when continually exposed to fish flesh, are absorbed into the meat over time and impart a smoke flavor to the flesh. The smoke compounds act as a natural xe2x80x9cbacteriostatxe2x80x9d and greatly increase the refrigerated shelf life of the flesh (up to three times the un-smoked shelf life). Smoking of fish increases the shelf life by killing a majority of the bacteria initially present, and then creating an acidic environment that slows the growth of bacteria over time in refrigerated conditions. The compounds in the smoke that are primarily responsible for the extension of the shelf life of fish are the aldehydes and phenols, as well as CO, CO2, NO, NO2, which are the main gaseous components of smoke. These compounds maintain the xe2x80x9cfreshxe2x80x9d color of the fish, as well as prevent the growth of bacteria both on the surface of the fish and within the flesh.
However, one of the problems inherent in smoking fish products to impart preservation properties is that the smoke odor and/or smoke taste remains present in the fish flesh. Additionally, smoke that is produced from organic fuel materials typically contains particulates, such as creosote, tar, soot, etc., which are undesirable elements to have in contact with the fish product. Thus, it is beneficial to provide a smoke that has had some of the particulate removed and further remove the smoke odor/taste while still maintaining the extended shelf life.
U.S. Pat. No. 5,972,401 to Kowalski discloses a process for manufacturing a tasteless, super-purified smoke for the treatment of seafood and meat. The super-purified smoke is then applied to seafood or meat to preserve the freshness, color, texture, and natural flavor, particularly after the seafood or meat is frozen and thawed. Kowalski teaches that the smoke must be super-purified by filtering out a substantial amount of odor and taste imparting particulate matter and gaseous vapors, thereby recovering the smoke in a tasteless form. Thus, Kowalski is limited in that it requires that the smoke be super-purified into a tasteless form in order to prevent the impartation of the smoke odor or taste to the seafood or meat products.
U.S. Pat. No. 5,484,619 to Yamaoka discloses a process for smoking fish and meat at low temperatures, thereby conferring a smoked flavor and taste, and further preventing decomposition and discoloration of the fish or meat. As in Kowalski, the smoke is filtered to remove the larger particulates and provide a smoke that will preserve, sterilize and aid in maintaining the color of the flesh of the fish or meat. However, Yamaoka teaches that the smoke odor or taste will remain in the fish or meat and that the temperature of application of the smoke is important. Specifically, the Yamaoka smoke preservation process must be carried out at extremely low temperatures (between 0 and 5xc2x0 C.) in order to maintain the freshness and quality of the fish or meat products Therefore, Yamaoka is limited to a smoke process for preserving fish or meat products wherein the product will retain a smoke odor or taste, and the process is further limited to a narrow range of temperature conditions.
U.S. Pat. No. 2,120,237 to Brenner et al. discloses a method for partially drying and then smoking fish fillets to preserve them. The fish fillets were first dried to remove a substantial portion of the moisture present and then treated within a smoke atmosphere. This method imparted a smoke flavor to the dried fillets and aided in the prevention of the fish deterioration.
It is also known to preserve the freshness or color of fish or other meat products by several other methods of treatment. U.S. Pat. No. 3,859,450 to Alsina teaches that melanosis (blackening) in shellfish is prevented by application of an innocuous acid solution followed by carbon dioxide gas. The resultant chemical reaction between the acid solution and the carbon dioxide produces carbonic anhydride that penetrates the shellfish and prevents melanosis during preservation by freezing. The process also discloses that the use of a food preservative, such as metabisulphite, will prolong the preservation of the original taste and texture of the shellfish after thawing.
U.S. Pat. No. 4,522,835 to Woodruff et al. discloses a process for maintaining good color in meat, poultry and fish products. Specifically, Woodruff teaches that subjecting the product to an atmosphere containing a low oxygen concentration and followed by an atmosphere containing a small amount of carbon monoxide will convert oxymyoglobin to carboxymyoglobin. The process produces a red color in the product and permits lengthy refrigeration of the product (two to three weeks). Further preservation is accomplished by Woodruff by maintaining the product in a modified carbon dioxide atmosphere or by freezing.
U.S. Pat. No. 5,540,942 to Tokoro teaches that the freshness of meat or fish may be improved by treatment with ubidecarenone to prevent discoloration of the product. The ubidecarenone additive prevents the oxidation of the haem pigments, thereby maintaining the red color of xe2x80x9cfreshxe2x80x9d product by preventing discoloration to a brown or gray appearance.
Ozone, a GRAS (generally regarded as safe) substance, has been used for more than ten years to sanitize, deodorize and prevent bacterial growth in food items. Its main strength is in the killing of surface and subsurface bacteria that lead to decomposition of fish flesh during refrigerated storage. Ozone may be applied using a gaseous or liquid medium or a combination thereof.
U.S. Pat. No. 5,783,242 to Teague discloses a process of treating poultry with ozone and ozone dissolved in water to reduce the population of contaminating organisms. The product is first subjected to a solution containing ozone and then exposed to a gaseous atmosphere containing ozone. The product is also subjected intermittently to UV exposure which further acts as a bactericide and decomposes any ozone remaining on the product into oxygen.
Although, it is known that the foregoing techniques may be used to preserve the fish flesh itself, these techniques often result in an appearance of fish that has lost its xe2x80x9cfreshxe2x80x9d attributes. Accordingly, without the xe2x80x98pinkxe2x80x99 or xe2x80x98redxe2x80x99 color of the fish flesh, consumers often consider such preserved fish as xe2x80x9cnot fresh,xe2x80x9d resulting in a lower sales price for the fish. The foregoing techniques claim to maintain the color of the fish do so with the addition of chemical additives and preservatives which can alter the taste and texture of the fish or be toxic in certain dosages to humans. Additionally, maintaining the xe2x80x9cfreshxe2x80x9d attributes of the fish is not taught when the fish is preserved or further preserved by freezing.
Therefore, a heretofore unaddressed need exists in the industry to satisfy the aforementioned deficiencies and inadequacies and provide a preserved fish that retains all of the qualities and characteristics of a xe2x80x9cday caughtxe2x80x9d fish.
Through research and product development, the inventors have devised a process for fish preservation that results in the production of an extremely high quality, fresh seafood product line with extended shelf life characteristics. The fish products are preserved using smoke and ozone so as to maintain the qualities and characteristics of freshly caught fish.
The process allows the transportation of fresh and frozen seafood items from remote areas of the world in a safe, sanitary and economical way. However, Applicants"" preservation process has overcome the drawbacks of typical freezing techniques and allows the consumer to receive a high quality, extremely safe fish with the taste, texture and attributes of freshly caught fish. The fish appears xe2x80x9cfreshxe2x80x9d to consumers as it retains its red, or bright, color and is, thus, more appealing.
In general, the process includes the steps of smoking of fresh fish, treating it with ozone and optionally freezing the fish. When a smoke and ozone process is utilized, the shelf life is extended and the fish retains more of its xe2x80x9cfreshxe2x80x9d color. The smoke/ozone process retains the xe2x80x9cfreshxe2x80x9d color and extends shelf life of the fish flesh by binding the carbon monoxide molecule to the heam pigment in the hemoglobin molecule in such a way that it takes much greater than normal oxidative force to oxidize the hemoglobin molecule. Furthermore, the smoke/ozone process aids in the prevention of bacterial decomposition and maintains the hemoglobin molecule (red color) during freezing and frozen storage by binding it with a CO molecule.
Optionally, the smoke/ozone process can include the steps of wiping the flesh of the fish with alcohol one to three times during the preservation process, before or after smoking the fish. The application of alcohol to the exterior of the fish kills surface and shallow bacteria on contact with the alcohol. The fish would be placed in a modified xe2x80x9csmokexe2x80x9d atmosphere for 1 to 72 hours, with the length of time depending on the thickness of the fish product, with thicker products requiring more time than thinner products. If the smoke is applied to the fish while in a vacuum chamber, the time required for the smoke application can be reduced to less than a minute. During the smoking step, a vast majority of xe2x80x9caerobicxe2x80x9d bacteria die as there is no oxygen available for them to breathe. The smoking step additionally creates an acidic pH in the fish by the dissolution of free carbon dioxide, present in the smoke, into the fish. The acidic pH prevents the growth of bacteria during the xe2x80x9cfreshxe2x80x9d stages of the process. An optional final step can involve freezing the product to kill an additional percentage of the bacteria present on the product The fish product can be initially prepared into appropriately sized sections or fillets in order to accelerate the smoke/ozone application steps.
With the use of this fish preservation process, the shelf life of the product is increased, usually from about 2-3 days after the product is landed to about 10-12 days. This increase in shelf life after the product has been treated allows the product to be shipped to remote areas requiring longer shipping times. Also, the final processing of the product into consumer-ready forms, including cutting, portioning and packing the product, can be performed at the central processing facility. This avoids the necessity of having to perform the final processing of the product at the store level.
Other processes, systems, methods, features and advantages of the present invention will be or will become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional processes, systems, methods, features and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.